diff --git a/packages/datadog-api-client-common/http/isomorphic-fetch.ts b/packages/datadog-api-client-common/http/isomorphic-fetch.ts
index 67a1e3957a4a..f296b0b856d2 100644
--- a/packages/datadog-api-client-common/http/isomorphic-fetch.ts
+++ b/packages/datadog-api-client-common/http/isomorphic-fetch.ts
@@ -171,14 +171,17 @@ export class IsomorphicFetchHttpLibrary implements HttpLibrary {
     for (const header in originalHeaders) {
       headers[header] = originalHeaders[header];
     }
-    if (headers["DD-API-KEY"]) {
-      headers["DD-API-KEY"] = headers["DD-API-KEY"].replace(/./g, "x");
-    }
-    if (headers["DD-APPLICATION-KEY"]) {
-      headers["DD-APPLICATION-KEY"] = headers["DD-APPLICATION-KEY"].replace(
-        /./g,
-        "x"
-      );
+    // Mask credential headers before serializing for the debug log.
+    // Authorization carries Bearer tokens (delegated tokens, PATs). See CRED-2625.
+    const headersToRedact = [
+      "DD-API-KEY",
+      "DD-APPLICATION-KEY",
+      "Authorization",
+    ];
+    for (const header of headersToRedact) {
+      if (headers[header]) {
+        headers[header] = headers[header].replace(/./g, "x");
+      }
     }
 
     const headersJSON = JSON.stringify(headers, null, 2).replace(/\n/g, "\n\t");
diff --git a/tests/api/log-redaction.test.ts b/tests/api/log-redaction.test.ts
new file mode 100644
index 000000000000..454d8eee5547
--- /dev/null
+++ b/tests/api/log-redaction.test.ts
@@ -0,0 +1,47 @@
+import { IsomorphicFetchHttpLibrary } from "../../packages/datadog-api-client-common/http/isomorphic-fetch";
+import {
+  HttpMethod,
+  RequestContext,
+} from "../../packages/datadog-api-client-common/http/http";
+import { logger } from "../../logger";
+
+// TestLogRequestRedactsAuthorization verifies that when debug logging is on,
+// the IsomorphicFetchHttpLibrary masks the Authorization header (Bearer
+// tokens — delegated tokens, PATs) before sending the request log line to
+// the logger. Without this, callers running with debug logging and access-
+// token auth leak the bearer to stderr / CI artifacts / log shippers.
+// See CRED-2625.
+test("logRequest masks Authorization Bearer token", () => {
+  const debugMessages: string[] = [];
+  const originalDebug = logger.debug.bind(logger);
+  logger.debug = (...args: unknown[]) => {
+    debugMessages.push(args.map(String).join(""));
+  };
+
+  try {
+    const http = new IsomorphicFetchHttpLibrary();
+    http.debug = true;
+
+    const ctx = new RequestContext("https://api.example.com/ping", HttpMethod.GET);
+    ctx.setHeaderParam("DD-API-KEY", "api-key-secret-value");
+    ctx.setHeaderParam("DD-APPLICATION-KEY", "app-key-secret-value");
+    ctx.setHeaderParam("Authorization", "Bearer ddpat_supersecret_should_not_leak");
+
+    // logRequest is private; exercise it indirectly by reaching through the
+    // class. Acceptable in a test file since the redaction surface is what
+    // we're asserting on, not the public send() pipeline.
+    // eslint-disable-next-line @typescript-eslint/no-explicit-any
+    (http as any).logRequest(ctx);
+
+    const joined = debugMessages.join("\n");
+    expect(joined).not.toContain("api-key-secret-value");
+    expect(joined).not.toContain("app-key-secret-value");
+    expect(joined).not.toContain("ddpat_supersecret_should_not_leak");
+    // Each redacted value is replaced with `x` repeated to its original length.
+    expect(joined).toMatch(/DD-API-KEY":\s*"x+"/);
+    expect(joined).toMatch(/DD-APPLICATION-KEY":\s*"x+"/);
+    expect(joined).toMatch(/Authorization":\s*"x+"/);
+  } finally {
+    logger.debug = originalDebug;
+  }
+});